Auto close brackets addon not working

[GNHua]

I tried to add auto closing brackets addon from this codemirror example.

I added the addon javascript, and set autoCloseBrackets to be true for CodeMirror.

In the codemirror example, when a [ key is pressed, it generates [], and put cursor in the bracket.

The issue is that when I press [ key, it generates [][. The same goes for keys like {, (.